Move the QP scaling thresholds to the relevant encoders.

Also provide a new set of thresholds for the VideoToolbox encoder. The new thresholds were experimentally determined to work well on the iPhone 6S, and also adequately on the iPhone 5S.

BUG=webrtc:5678

Review-Url: https://codereview.webrtc.org/2309743002
Cr-Commit-Position: refs/heads/master@{#14420}
diff --git a/webrtc/api/android/jni/androidmediaencoder_jni.cc b/webrtc/api/android/jni/androidmediaencoder_jni.cc
index 8d0d3b5..e84b850 100644
--- a/webrtc/api/android/jni/androidmediaencoder_jni.cc
+++ b/webrtc/api/android/jni/androidmediaencoder_jni.cc
@@ -395,16 +395,9 @@
   ALOGD << "Encoder automatic resize " << (scale_ ? "enabled" : "disabled");
 
   if (scale_) {
-    if (codecType_ == kVideoCodecVP8) {
-      quality_scaler_.Init(
-          QualityScaler::kLowVp8QpThreshold, QualityScaler::kBadVp8QpThreshold,
-          codec_settings->startBitrate, codec_settings->width,
-          codec_settings->height, codec_settings->maxFramerate);
-    } else if (codecType_ == kVideoCodecH264) {
-      quality_scaler_.Init(QualityScaler::kLowH264QpThreshold,
-                           QualityScaler::kBadH264QpThreshold,
-                           codec_settings->startBitrate, codec_settings->width,
-                           codec_settings->height,
+    if (codecType_ == kVideoCodecVP8 || codecType_ == kVideoCodecH264) {
+      quality_scaler_.Init(codecType_, codec_settings->startBitrate,
+                           codec_settings->width, codec_settings->height,
                            codec_settings->maxFramerate);
     } else {
       // When adding codec support to additional hardware codecs, also configure